Various topologies are known for enabling data communications between various computing components. Two common topologies are the bus and star topologies. Bus topologies use a multi-drop configuration to connect a variety of resources. For example, processing, memory, and input/output (I/O) components may be interconnected with a bus, using the bus to transfer data between the different components. Such a bus is commonly incorporated into a backplane that is used to interconnect different components. In systems requiring relatively high amounts of data transfer, however, bus topologies can limit system performance. For example, bus-based architectures using present day bus technology generally have a limit of approximately 2 Gigabits/second (Gbps) per backplane bus. Thus, systems requiring higher throughput may employ multiple backplane busses, which can present I/O challenges. Furthermore, bus architectures may present reliability concerns, as any resource on the bus can compromise the integrity of the whole system. In systems requiring high reliability, this can be a significant design consideration. For example, in a space environment, radiation effects may require that various electronic designs be capable of high-reliability even in the event of detrimental radiation effects on the electronic systems.
For example, radiation effects on electronics systems in a space environment generally fit into one of two categories, destructive (permanent) or non-destructive (not permanent). Destructive radiation effects, for the types of components as would be typically used to construct this type of system, may include single event latchup (SEL) and total ionizing dose (TID). Other destructive effects may also include single event dielectric rupture (SEDGR), single event gate rupture (SEGR) and single event gate burnout (SEB). Single event type errors can occur at any point in the mission duration. TID is a cumulative effect is generally more likely to occur later in a mission. Non-destructive radiation effects include single event upset (SEU), single event functional interrupt (SEFI), and single event transient (SET). SEU, SEFI and SET generally require mitigation at the system level. Some classes of these errors may require ground intervention. In any event, high reliability systems to be used in such applications may be required to continue operation after such events.
Traditional star topologies include multiple nodes that use point-to-point connections from each node to send/receive data from a central resource or switching function. Data transfer may be accomplished through data packets that comprise a header portion that instructs the switching function as to the destination node of the packet. In traditional star topologies, each packet sent by a node must pass through the switching function so that switching function can route the packet to its destination node. The switching function in such networks may be incorporated in a switch card in a chassis, for example, which provides the data/packet distribution for the system. Each node in such a star system may be an individual payload or a sub-network, and can be a leg on a star of the next layer in a hierarchy. Star topologies require redundancy to provide reliability. Reliance on a single switching function can cause a loss of all elements below a failure point. Dual star topologies may be used for high availability applications. However, even in a dual star configuration, the star topology still has a “choke” point that may restrict the speed and efficiency of packet transfer and may create a potential failure point within a network. In applications that require high reliability and high availability, a failure in such a network may not be able to be tolerated.